Microsoft has joined the public opposition to SOPA, although like Google and many other opponents, won't black out its site today. Although some people have said Microsoft's opposition is insincere or half-hearted, the company has been quietly working against it behind the scenes at least since November.

Bloomberg reports that Microsoft has said in a statement, "We oppose the passage of the SOPA bill as currently drafted. Hundreds of millions of customers rely on our services every day so we dont plan to shut those down to express our view."

"We think the White House statement points in a constructive way to problems with the current legislation, the need to fix them, and the opportunity for people on all sides to talk together about a better path forward."

The White House statement that Microsoft is referring to criticizes SOPA for a variety of reasons, including shutting down sites violating the copyright law, by using the Domain Name System, and says, "Any effort to combat online piracy must guard against the risk of online censorship of lawful activity and must not inhibit innovation by our dynamic businesses large and small."

There's a segment of Internet users who will never believe Microsoft's sincerity on any issue, and don't believe it on this one, either. But they're wrong. It appears that Microsoft has been working behind the scenes against SOPA at least since November. CNet reported in late November:

Microsoft has long been one of the most ardent proponents of expanding U.S. copyright law. But that enthusiasm doesn't extend to the new Stop Online Piracy Act, which its lobbyists are quietly working to alter.

In addition, the article reports, Microsoft convinced the Business Software Alliance, of which it is a member, to change course and oppose SOPA after the alliance had originally supported it.

Microsoft would potentially gain financially if SOPA were passed, while many other opponents, such as Google, wouldn't be financially hit. So Microsoft deserves credit for doing the right thing in its opposition.